Numerous consumer products are available for the laundering of household/domestic fabrics. Similarly, many products exist that may be added during the rinse cycle of standard washing machine cycles or in domestic dryers that will deposit softening and/or other care actives onto the fabrics. This type of two or three step process has become very common for those consumers looking for both excellent cleaning and fabric softening. However, this two or three step process is more time-consuming and costly than a single wash-added product. More recently, due to consumer demands, manufacturers of laundry detergent products have sought to provide one product that provides both cleaning and fabric care benefits such as softness, through the wash.
It is important to realize, however, that these two goals (cleaning and softness) are traditionally diametrically opposed. Cleaning of fabrics typically results in the removal of dirt, allergens, stains, and other deposited materials. In contrast, providing a care benefit (such as a soft fabric feel) typically results from the deposition of beneficial care actives onto the fabrics. It is therefore difficult to simultaneously clean (remove) and soften (deposit) fabrics through the wash. In the past, it has been recognized in through the wash cleaning and care products that deposited care actives may entrap dirt or other materials onto the fabrics, resulting in a dingy appearance that is obviously undesirable to consumers. The deposited care actives may also themselves leave visible residue if they do not deposited evenly over the fabric surface. Similarly, it has been seen that the care actives are not deposited at all or are removed by the cleaning ingredients.
More recently, it has been recognized that low levels of cationic polymers, termed “cationic deposition aids” are capable of improving deposition onto fabrics of a range of desirable benefit agents, for fabric softening, perfumes, anti-wrinkle agents, hueing dyes, and the like. Such cationic deposition aids are described the art and fall generally into two classes: (1) “natural” types comprising a carbohydrate moiety, such as cationic hydroxyethylcellulose or cationic guar gum; and (2) “synthetic types” comprising cationic moieties but no carbohydrate. These “synthetic types” are exemplified by copolymers of polyacrylamide (PAM) and methacrylamidopropyltrimethylammonium chloride (MAPTAC). One difficulty with the “natural” types is their incompatibility with laundry detergent enzymes, especially enzymes having some degree of cellulase activity.
Furthermore, it has now been discovered that synthetic cationic deposition aids comprising cationic and uncharged (nonionic) monomers in the absence of anionic monomers at the pH of laundry washing tend to leave unsightly residues on laundered fabrics. These residues are easily visualized by the human eye when the laundered fabrics have a dark color. However, these findings are surprising in that prior disclosures of similar materials, such as U.S. Pat. No. 6,949,498, provide only indiscriminate lists of cationic polymers in liquid laundry detergents. Such disclosures only provide a measure of fabric softness benefits associated with the cationic polymers without any suggestion of visible residues, much less any disclosures of how to remedy such problems.
Accordingly, it would be highly desirable to identify improved laundry detergents comprising selected polymers capable of providing care benefits through the wash to fabrics while maintaining good cleaning and avoiding unsightly residues.